Wheel Speed Sensor

PURPOSE
Rotating movement of the road wheels (wheel speed) is transmitted to the Antilock Brake System (ABS) control unit via four wheel speed sensors.

CONSTRUCTION
The speed sensors consist primarily of a magnetic core and a coil. The pole is surrounded by a magnetic field.

For the front axle, the signal transmitters are arranged axially and require no adjustment. They are installed in the stub axles, with the gearwheel which generates the actual impulses pressed into the front axle hub.

At the rear axle, the sensors are attached to the wheel hubs between the two wheel bearings, and the pulse-generating gearwheel is integrated into the spacing sleeve used on the wheel bearings.

OPERATION
As the wheel revolves, the teeth of the gearwheel move through the magnetic field. This varies the magnetic flux and induces a voltage in the coil of the speed sensors. The frequency of the pulses generated by the successive teeth is proportional to the speed of rotation of the road wheel.